1) Get the Clymer. The Owner's manual is fairly useless. The factory service manual is good but I think the Clymer is written for the layman whereas the service manual assumes you know what you're doing.
2) Ditto on the no lube, just WD40 for periodic cleaning and preventing rust on the outside of the chain. O ring chains are sealed and no fancy lube is getting inside - wattman's testing is proof enough for me. Do NOT overtighten the chain. This and overtightening the oil drain plug are two of the most common newbie mistakes. Having the chain too tight is hard on the wheel bearings and output shaft bearing and seal.....best case is a leak, worst case and you're taking your bottom end apart. A quick check is that you should be able to touch the chain to the front underside of the rubber slipper (where the slipper ends on the bottom) on the swingarm but NOT be able to touch the aluminum itself.
3) The counterbalance adjuster lever (fondly known as the "doohickey") is a known weak link on the KLR, particularly the Gen1. I strongly recommend NOT adjusting the doohickey until you've taken the cover off and verified that the lever is still in one pce and the spring is intact and has tension.....if you adjust it without checking there is a strong possibility that these parts have failed and instead of taking slack out of the chain, it will increase the slack......sometimes to catastrophic levels. Replacing the factory doohickey lever and spring is the only modification that NEEDS to be done to a Gen1 KLR IMO. Eagle Mfg & Eng
for a replacement c/w torsion spring so the problem is dealt with forever. I keep the broken lever from my 2001 on my keychain as a reminder.....
Have fun and keep the shiney side up, :-)